JPH0435178B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Field of Industrial Application This invention is used for dental treatment, and is used to take panoramic tomographic images of not only the dentition area but also the oral function and the facial area including the upper and lower jaws. In particular, the present invention relates to a dental full-mouth X-ray imaging device that can obtain images close to actual size and with excellent sharpness by shortening and making the distance between the object and the image receiving surface substantially uniform.

(2) Prior art The dental full-mouth X-ray imaging device (hereinafter referred to as a panoramic device) which has been widely used in the past has a fixed relative distance between the X-ray source and a cylindrical or flat cassette holder, and a single horizontal cassette holder. It is installed vertically at both ends of the arm. When this horizontal arm is suspended from a rotation mechanism such as an elliptical or pseudo-elliptical orbit system or a three-arc compound orbit system and rotated along the dental arch of the examinee, the image layer, that is, the tomographic area The dental arch is limited to a pseudo-elliptic continuous curve, and the temporomandibular joint area is mostly
This makes it difficult to capture images of the temporomandibular joints as sharp as those of the dental arches. For this reason, conventional panoramic devices make the feeding speed of the cassette of the cassette holder faster than the rotation speed of the horizontal arm in the temporomandibular joint area, and return it to a speed synchronized with the arm rotation speed in the dental arch area. It is customary to perform so-called variable cassette feed rate control to form one continuous tomographic region between the dental arch and the temporomandibular joint. The cassette feed rate variable control means may include, for example, a cam plate having a protrusion formed in a shape similar to the series of fault areas, and a friction transmission mechanism to control the cassette feed rate at a variable speed corresponding to the rotational phase of the horizontal arm. Therefore, mechanical interlocking systems that control cassette feeding are often used. In addition, in recent years, various motor-driven devices have been devised in which the cassette holder is equipped with a drive motor dedicated to feeding the cassette, and the cassette feeding is controlled at a variable speed corresponding to the rotation phase of the horizontal arm. However, it is becoming popular due to its simple mechanism and excellent variable controllability. However, panoramic devices equipped with either the mechanically interlocked type or the motor-driven cassette feed variable control mechanism can simultaneously take tomographic images of the dental arches and temporomandibular joints. Therefore, there is a major drawback in that images with different enlargement ratios of, for example, 15 to 20% are mixed together. FIG. 1 is a schematic diagram illustrating this. The horizontal arm 1 is rotated by, for example, a single-axis continuous movement rotation mechanism 2, and the feeding speed of the cassette 4 of the cylindrical cassette holder 3 in the direction of arrow 5 is controlled by the mechanical or motor type cassette feeding control. is made variable. The distance (La) between the focal point 7 of the X-ray tube 6 and the cassette 4 (synonymous with X-ray film) is normally 520 to 550 mm, and in this example is 530 mm. With this configuration, the suspension shaft 8 of the horizontal arm 1
The planetary gear 9, which is integral with the fixed sun gear 10, is inscribed in the fixed sun gear 10 and revolves in the direction of the arrow 12 while rotating in the direction of the arrow 11, whereby the dental arch fault trajectory 14 of the lower jaw 13 and the temporomandibular joint fault trajectory 15, 15' are photographed continuously. However, horizontal arm 1 (1a)
In the rotation process (1b), when the cassette 4 rotates along the pseudo-elliptical trajectory shown by the two-dot chain line 16, the
While the distance between the focal point and the cassette (La) of 530 mm remains unchanged, the distance (Lc) between the subject at the end of the right temporomandibular joint (15T) and the cassette 4 changes, for example, to a minimum value of about 30 mm (Lc ₁ ). It increases with movement, reaches the right second molar 17, and reaches a maximum value (Lc ₂ ) of approximately 110 mm.
This (Lc ₂ ) does not change during the dental arch trajectory 14,
After passing the left second molar 17', it begins to decrease again.
Return to the above minimum value (Lc ₁ ) at the left temporomandibular joint end (15T'). In other words, even though the rotation range of the temporomandibular joint tomographic areas 15 and 15' is narrow, the magnification of the subject changes continuously by approximately 20% to 1.061.26 as in this example, resulting in a special image that is sharp. The degree of sensitivity varies depending on the location, and the disadvantage is that only images with extremely low diagnostic accuracy can be obtained. Furthermore, the expansion rate does not change in the dental arch, but as shown in Figure 1, the temporomandibular joint trajectory 1
5 and 15' are spread to the left and right, so even if it is placed as close to them as possible, the rotation trajectory 16 of the cassette 4 will not be the same.
Since it is fixed, it is inevitable that the distance from the tooth row (Lc ₂ ) will be about 10 cm or more.

This is considered to be one of the factors that hinders the improvement of the sharpness and resolution of dental arch images, particularly in the anterior tooth region, with conventional devices.

(3) Purpose The purpose of the present invention is to reduce the distance between the cassette and the subject as much as possible, and to make the distance almost uniform, in order to solve the problems and drawbacks of the conventional panoramic device described above. To provide a dental full-mouth X-ray device capable of taking panoramic images of images at a substantially constant magnification rate, obtaining sharp images close to actual size, and having excellent resolution.

(4) Configuration Next, the gist of the configuration of this invention will be described.
The apparatus according to the present invention is no different from the conventional panoramic apparatus in terms of tomography principles and basic configuration. The first major difference is the structure that allows the relative positions of the cassette holder vertically disposed on the horizontal arm, the horizontal arm suspension shaft, and the X-ray source to be moved. In other words, in the case of a device having a mechanically interlocked variable cassette feed mechanism, the vertical side arm of the cassette holder is extended and retracted together with the transmission part of the above mechanism provided on the horizontal arm, and in the case of a device having a motor-driven variable cassette feed mechanism. move the cassette holder alone, or extend and retract the end of the arm on which the cassette holder is suspended. The second difference is that the cassette of the cassette holder is brought close to the head and facial features, and the cassette rotates along a trajectory that corresponds to the rotational phase of the horizontal arm, that is, each part of the facial features, and approximately approximates the surface of the facial features. For example, a cam or a motor is used to control the relative positions of the cassette holder, the horizontal arm suspension shaft, and the X-ray source.

(5) Embodiments Examples of the present invention will be described below with reference to the drawings. FIG. 2 is a side (partially cross-sectional) view of the horizontal arm rotating portion of a panoramic apparatus according to the first embodiment of the present invention in which variable cassette feed control is mechanically interlocked. The pedestal 20, which incorporates the arm rotation mechanism 2 and is movably attached to the base of the device (not shown), has a fixed sun gear 10 (see Fig. 1) of the rotation mechanism 2 on its upper part while maintaining its inscribed contact with the fixed sun gear 10 (see Fig. 1) of the rotation mechanism 2. A revolution mechanism 21 for causing the planetary gear 9 to revolve around the center of the sun gear 10 is provided. When the rotation motor 22 rotates, the rotation mechanism 2 is regulated by the revolution mechanism 21 and rotates on the mount base plate 24 via the wheels 23, and the horizontal arm 1 integrated with the planet gear 9 rotates. The suspension shaft 8 is rotated, for example, by 220 degrees as shown in FIG. Fixed to the lower surface of the substrate 24 are a cassette drive mechanism, that is, a variable cassette feed rate control mechanism, and a cassette rotation control cam plate 25, which is one of the essential parts of the present invention. First, the former cassette feed drive mechanism, that is, the mechanically interlocked speed control mechanism 26 mentioned above will be briefly explained. When viewed from below, the ∧-shaped protrusion 27 formed on the cam 25 approximately approximates the tooth-jaw fault trajectory of 15, 14, and 15' shown in FIG. The central shaft 29 is pivotally supported by a bearing 30 of a bearing stand fixed on the horizontal arm 1, and a small diameter friction ring 31 is fixed to the other end. Furthermore, the friction ring 31 is in contact with a large diameter friction roller 32 that is directly connected to the cassette rotation shaft of the cassette holder 3. This configuration enables variable control to correspond to the rotational phase of the horizontal arm 1, for example, synchronizing the cassette feeding speed with the arm rotational speed in the dental arch area, and increasing the cassette feeding speed in the temporomandibular joint area. It will be done. Next, the latter, that is, the cassette rotation control mechanism 33 using the cam plate 25 will be described. First, in order to make the horizontal arm 1 extendable and retractable, the horizontal arm 1 is separated into the cassette holder hanging side arm 34 and the hanging shaft and X-ray source hanging side arm 35, each formed into a rectangular tube shape, for example, and the movable arm 34 into the fixed arm 35. The fixed arm 35 is configured to be able to easily and slidably support a movable arm 34, which is a cantilever beam that receives a concentrated load at its free end. For example, in order to reduce the coefficient of friction between the two, there are two locations, one at the end of the fixed arm 35 and the other at a predetermined distance therefrom, which are generally called balls or bushes, and have a large number of balls along the axial movement of the shaft they support. A bearing 36 is provided in which the balls roll and circulate through the cage. End 37 of movable arm 34
Several spring stops 38 are provided on the fixed arm 35 side, and several tension helical springs 39 having an appropriate spring constant are provided between them and the same spring stop 38' on the fixed arm 35 side. A support 40 is installed on the upper surface of the movable arm 34, slightly out of phase with the cylindrical body 28, by, for example, welding, and a wheel 41 is rotatably supported on this support. This wheel 41 is the tension spring 3
9 is the cassette rotation control cam plate 25 described above. The cam plate 25 has the above-mentioned ∧-shaped protrusion 26 formed on its lower surface, and its side surface is a cam plate having an arbitrary shape.
Here, as shown in Fig. 3, the cassette rotation control cam plate 2 is
5 will be explained. Figure 3 is a plan view of the human skull seen from above, especially showing the lower jaw tooth row and temporomandibular joint.
The relationship with the cheekbones is shown, and other parts are omitted. Cheekbone 43, lower jaw 13 and skull 44
The dotted line on the outer periphery is the skin part 45, (45T)
indicates a nasal convexity. Due to the revolution of the planetary gear 9 shown in FIG. For example, the pseudo-elliptical locus 16 is rotated in the direction of arrow (C). For example, divide this rotation into 20 parts (3
-0) to (3-20). As explained in FIG. 2, the relative position between the cassette holder 3 and the horizontal arm suspension shaft 8 can be changed, so that the film (F) in the cassette 4 and the above-mentioned axis (8C) are aligned as shown in FIG. The distance (Lb) from the cam plate 25 can be variably controlled in any manner corresponding to the rotational phase depending on the shape of the cam plate 25. For example, if the cassette holder 3 is to be rotated along a trajectory 46 of (F ₀ ) to (F ₂₀ ) that is close to the facial features and approximately approximates the facial plane as shown in FIG. Corresponding to the dynamic phase, the facial appearance approximation locus 46 may be modified by the shape of the cam plate 25. For example, the phase (3-
0), if the amount of movement (l) of the movable arm 34 in the direction of arrow (d) (this direction is the opposite direction (e) after phase (F ₁₅ )) is adjusted to zero in advance. Although it varies depending on the configuration of the rotation mechanism, the movable arm 34
The maximum amount of movement (lmax) is several centimeters, and the mechanism described above allows for smooth operation. On the other hand, the facial appearance approximation trajectory 46 is almost parallel to the tomographic trajectory that includes the temporomandibular joints 15, 15' and the dental arch 14 as a series of tomographic regions, and the magnification of the tomographic image is approximately 110% on average. , and the variation in magnification rate for each part is at most 5%
It stops within. Next, a second embodiment of the present invention will be described with reference to FIGS. 4 to 7, that is, a panoramic apparatus in which the cassette is driven by the motor drive method described above and the cassette rotation control means is an electric type 47. FIG. 4 is a side view of the photographing section of the above-mentioned apparatus, and as shown in FIG. 2, the pedestal 20 has a built-in rotating mechanism 2 and is supported by the main pillar of the apparatus (not shown) so as to be able to rise and fall. The suspension shaft 8 of the rotation mechanism 2 is the fixed arm 1 on the side of the horizontal arm 1 on which the X-ray source 6 is vertically mounted.
8 is suspended, and the fixed arm 18 is, for example, a movable arm 19 on the side on which the flat cassette holder 3' is suspended.
Supports the support so that it can expand and contract. The head positioning mechanism 48 is fixed to the pedestal 20 via a support 49, and fixes the subject's head indicated by a dashed line 50 in a fixed position.
For example, a pulse motor 52 dedicated to feeding the cassette is installed inside the cassette holder 3', and moves the flat cassette 4' in a direction perpendicular to the X-ray radiation cone axis at a movable speed corresponding to the rotation phase of the horizontal arm. It is configured to allow This is a motor-driven cassette drive mechanism 51. Therefore, there is no need to provide a cassette drive mechanism on the movable arm 19. The figure shows the positioning of the head of the subject 50 and the phase of photographing the front teeth during panoramic photographing, with the cassette 4' being in the closest position to the facial features. The position of the movable arm 19 indicated by a one-dot chain line 19' indicates the cassette holder position corresponding to the left and right temporomandibular joints. Therefore (lmax)
is the maximum movement distance of the movable arm 19 mentioned above. FIG. 5 is a partially cutaway plan view of the top cover of the pedestal 20 shown in FIG. Through large diameter for example diameter approx.
A 200 mm friction rotating body 54 is rotated. As this rotating body 54 rotates about a few times, the arm suspension shaft 8 rotates through a rotation angle α, for example, about 220°, while rotating up to 8' via a transmission mechanism (not shown). If a ring plate 55 having, for example, 1 mm pitch unevenness (the unevenness is shown as a part of the figure for simplicity) is provided over the entire periphery of the large-diameter rotating body 54, and a pulse signal is outputted by an optical encoder 56. , the rotational phase of the horizontal arm 1 can be detected with high precision of 0.17° per pulse. This is the arm rotation phase detection means detailed in the specification of Utility Application No. 59-009828 "Arm rotation device for dental X-ray panoramic device" which the authors devised and filed earlier. is a part 47A of the cassette rotation control means 47 which applies the detection signal of 0.17°/pulse to the rotation control of the cassette holder. Then the 6th
Turning now to the figure, the figure is a partially cutaway plan view of the upper cover of the horizontal arm 1 of FIG. This shows the configuration of

The fixed arm 18 and the movable arm 19, which are integral with the suspension shaft 8, are engaged with each other through a pair of guide shafts 58 so as to be extendable and retractable. The guide shafts 58 are each supported by a pair of fixed stands 59 provided on the movable arm 19, and bearing stands 60, 61 on the fixed arm 18 side.
The shaft is slidably supported in the axial direction by two bearings. Further, an arm telescopic drive reversible motor 63, which is a pulse motor, for example, is fixed to a motor support stand 62 installed on the fixed arm 18 side, and its drive shaft 64 is connected to a bearing of the motor support stand 62 and a bearing stand 65. It is pivoted and has a threaded rod 6 at its tip.
7 are connected as one body. A cylindrical nut member 68 screwed onto this threaded rod 67 is fixed to the movable arm 19. With the above configuration, the motor 63 reversibly rotates at a rotation speed corresponding to the arm rotation phase detection signal, so that the movable arm 19 is rotated by the arrow
(f) Move a predetermined amount in each direction. In the figure, a dashed line 19' indicates the position of each part at the time of maximum movement. FIG. 7 is a block diagram of the digital control circuit (the remaining part 47C of the cassette rotation control means 47) of the rotation phase detection means of FIG. 5 and the cassette holder position control means of FIG. Since the large-diameter rotating body 54 is rotated at a constant speed by the pulse motor 22, the output signal of the encoder 56 is a pulse signal (S ₁ ) with a constant pulse interval.This signal (S ₁ ) is sent to the arm phase detection circuit 70. At the same time, the same signal is input to the aforementioned cassette feed speed control system circuit group 71, but a description of this 71 and its drive motor 72 will be omitted as they are not directly related to this invention.The phase detection circuit 70 is, for example, a pulse counter. By counting the number of pulses of (S ₁ ), the arm rotation phase is continuously detected in units of 0.17°, and the absolute position signal (S ₂ ) is stored as a digital signal of, for example, 10 pits in the cassette trajectory memory 73. This signal (S ₂ ) is also input to 71 like the above (S ₁ ).The cassette trajectory memory 73 stores in advance the facial appearance approximation trajectory 46 shown in FIG. 3 at every arm phase of 0.17°. The address is specified by the above (S ₂ ), and _the trajectory data (S ₃ ) is output. S ₄ ) and input to the pulse motor drive circuit 75.
The pulse motor 63 shown in the figure is driven to rotate the film image receiving surface in the cassette 4 along the above-mentioned trajectory 46 (see FIG. 3).

Although the first and second embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the illustrations and explanations. For example, the cassette holder of the second mechanically interlocking device may be flat, and the cassette holder of the motor-driven device of FIG. 4 may be cylindrical. Further, the rotation mechanism may be of any type other than a uniaxial continuous movement type. Further, the facial appearance approximation trajectory 46 in FIG. 3 is not limited to the one shown in the figure, and various trajectories are possible. The structure in which only the cassette holder is movable with respect to the arm and the above-mentioned arm movable mechanism other than those shown in FIGS. 2 and 6 belong to the scope of the present invention. Furthermore, the present invention is applicable not only to a panoramic-only device but also to a panoramic device with a CEF.

(6) Effects Since this invention is configured as described above,
The distance between the subject of the tomographic trajectory photographed by the panoramic device and the film image-receiving surface can be shortened and made uniform as much as possible according to the facial features, and the low magnification of approximately 1.05 can be achieved over the entire area of the teeth and jaws. By keeping the image constant, the image of the anterior tooth region, which has been a problem in the past, is close to the actual size, and image quality with excellent sharpness and resolution can be easily obtained, providing a convenient device with high diagnostic accuracy. It is.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating variation in magnification of a conventional panoramic device, FIG. 2 is a side view (partial cross section) of a horizontal arm rotating portion showing the configuration of a first embodiment of the device of the present invention, and FIG. The figure is a facial plan view showing the principle of rotation of the cassette of the device of this invention in a facial approximation trajectory, FIG. 4 is a side view of the photographing section of the second embodiment of the device of the invention, and FIG. 5 is the arm of the device. FIG. 6 is a plan view showing the rotation phase detection mechanism of the rotation mechanism, FIG. 6 is a plan view showing the extension and contraction mechanism of the horizontal arm of the above device, and FIG. 7 is a block diagram of the digital control circuit as the cassette rotation control means of the above device. It is a diagram. 1...Horizontal arm, 2...Rotating mechanism, 3, 3'
...Cylindrical/flat cassette holder, 4,4'...
...Cylindrical/flat plate cassette, 6...X-ray source, 8...
...Horizontal arm suspension/rotation axis, 26...Cassette drive mechanism (mechanical interlocking type), 51...Cassette drive mechanism (motor driven type), 19, 34...Movable arm on the cassette holder hanging side of the horizontal arm, 46...
A trajectory approximately approximating the face plane, 33...Cassette rotation control means by mechanical means using a cam, 47
A, 47B, 47C...Horizontal arm rotation phase detection means, and cassette rotation control means driven by a motor based on this detection means.

Claims (1)

[Scope of Claims] 1. A horizontal arm with an X-ray source at one end and a cassette holder placed vertically at the other end across the subject's head; and a cassette drive mechanism that moves the cassette of the cassette holder in the opposite direction of the arm rotation in accordance with the tomographic trajectory. In the apparatus, the cassette holder and the cassette drive mechanism are integrated into one unit, and the suspension axis of the horizontal arm and the relative position with the X-ray source are movable. 1. A full-mouth dental X-ray imaging device, comprising: a cassette rotation control means for rotating a cassette along a trajectory approximately approximate to the facial surface in accordance with the rotation phase of the dental full-mouth X-ray imaging device. 2. The dental full-mouth X-ray imaging apparatus according to claim 1, wherein the cassette rotation control means is a mechanical means using a cam. 3. The dental device according to claim 1, wherein the cassette rotation control means comprises horizontal arm rotation phase detection means and means for controlling the position of the cassette holder via a motor based on this detection signal. Chin X-ray device.